Depression as an emotional disorder is a very common entity among the aged. There are two problems related to this disorder in the geriatric population which are particularly unique: 1. The relationship between depression and dementia. 2. The nature of the depressive disorder itself. In the first problem, the physician is confronted with the differentiation between depression and dementia, since in the aged patient there are symptoms which are characteristic of both disorders. In the second problem, it has been suggested by previous investigators that depressive disorders in the aged are different than depression in the younger aged groups, in terms of its etiology, clinical manifestations, and clinical course. It is important that we can distinguish accurately between dementia and depression, since the latter is a treatable disease. The proposed study is an investigation of the relationship between depression, cerebral function, cognitive function and the social environment in the elderly (65 years old & over). We propose to study a number of variables on four populations of subjects (normal elderly, elderly with depression, with dementia, and with depression and dementia) in an attempt to develop descriptors and discriminators for these separate groups which can be used by all workers in the mental health area in their daily work. The variables which are to be studied longitudinally at 6-month intervals include: 1. Past medical history and physical illnesses, 2. Past life events, 3. Current emotional status with measures including depression, anxiety, emotional support, 4. Current social activities, 5. Cognitive function tests to document the actual quality and quantity of intellectual impairment, and 6. Cerebral function tests to include the electroencephalogram and cerebral blood flow, using the non-invasive technique, as a method of assessing cerebral impairment.